Man I should never say "I'm going to do it on this given day" because from that point forward, I curse myself.
Now where was I...
As to Unearthed Arcana and the addition of more races: I think you can take or leave the majority of them. Most of the races seem to stem largely from Gary's (published*) Greyhawk works. Wild Elves and Elves of the Vale of the Mage both stem almost directly from the '80 folio and '83 boxed set - but despite the officialness of the book, I think they (like a great many things in the book) can be discounted.
Class wise, even I find myself less enamored of the book. At this point, we have the Cavalier introduced now as a canon, by-the-book character class. Never in my campaign, never again. I've seen how ridiculous they can be. Moreover, they are mechanically clunky (as are "barbarians"), and while interesting from a role-playing standpoint, I would almost tend to want to add the fluff text for a Cavalier (NOT the rules) to the Paladin. Also they put the Paladin under the Cavalier class, which creates an interesting conundrum - by the book (and there is no admonition against it either in the book or in later errata) you can have an elven cavalier. While I realize to players of 2e and onward that may not seem strange, I for one would rule that out.
I never found the theif-acrobat particularly offensive, and would probably allow someone to play it in my campaign (as it is Greyhawk, after all...)
Magic items come mostly from published earlier modules - no foul here. Likewise, new spells and the treatment of spellbooks isn't very overpowering, so there's no problem with that for me.
The new unarmed combat methods are preferred over the old - Gary said he didn't think much of the method listed in the DMG. I've only ever known one player who could use them proficiently (and he doesn't like AD&D).
The last, and probably stickiest issue is the raising of the ceiling for demi-humans.
Now, I'm on record as feeling that demi-human level limits are a fine thing. Demi-humans are "front loaded" with plenty of bonuses - a triple-classed f/mu/th full elf with the stats to back up the classes, or even a dual-classed f/cl or mu/cl can be one tough customer. That's why I always admonish players who want to keep climbing levels in a campaign and do it playing demi-humans to play a (class)/thief. Fighter/thief, mu/th, etc. This is always a good route to go. You get the ever increasing thief abilities, ever increasing hit points, plus all the various bonuses as a demi-human that you got from the get-go. It's really a sweet deal.
With that in mind, I'm a little opposed to the level increase then, for the various races. I think that if for you it works to increase (or remove) demi-human level limits, more power to you. Just don't try to sell it to me.
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That's really just about it as far as it goes on UA, for me. I think it's a reasonable book that can be used largely as is. I think a good, thoughtful DM will consider each piece of it before integrating them into his or her campaign. Remember the last paragraph of the DMG, and don't get kneecapped by a player wielding this book and claiming that he should get to be an elven paladin triple specialized in bow with unlimited levels "just because"..
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all that you buy, beg, borrow or steal

